The invention concerns a hydraulically regulated and controlled vibration attenuator that is provided with a piston rod accommodated in a cylinder. The attenuating piston on the piston rod divides the cylinder into two compartments that are occupied by attenuating fluid. A bypass parallels the cylinder.
A vehicular attenuation system with an adjustable valve that makes it possible to vary the attenuation as desired during both the suction and the compression stages is known from German OS 3 434 877. An axially movable adjustable valve body is employed in conjunction with at least one pressure-controlled and spring-loaded valve positioned in series with it. The armature of the electromagnet is also a valve body.
An adjustable valve for a vibration attenuator is known from German OS 3 542 097. A slide in this valve can be selectively activated by electromagnets. German Patent 3 348 176 also describes a variable shock absorber that is electromagnetically controlled.
A vibration attenuator that has a control slide and is electromagnetically activated is known from German OS 3 832 625.
German OS 3 800 864 discloses a shock absorber with a constriction that can be varied. The cross-section of the constriction is dictated by way of electromagnetic controls with an annular armature.
None of these doouments, however, disclose mechanisms that can be employed with the "skyhook" principle known in controls technology. When a vehicle travels over an obstacle for example, the force of attenuation will initially have to be varied in only one direction of motion. The wheel must spring into position, with the result that the compression stage of the vibration attenuator must be soft enough to allow the wheel to spring in rapidly. The suction stage of the vibration attenuator must accordingly be hard enough to allow the wheel to spring back out again slowly, attenuating the vibration. A one-way valve that activates both stages can be employed in conjunction with this principle. When for example the vehicle's computer detects a high attenuating-piston speed in the compression-stage direction, it will have to open the valve to keep any impact on the body as weak as possible. What is of course important in this case is for the vibration attenuator to shift over when the attenuation piston is at the upper dead center. It is, however, extremely difficult in the given circumstances to determine the precise upper dead center. The result is constant impacts that are perceptible in the body.